This invention relates to a method of diagnosing aged degradation of oil-filled electrical equipments applied to determine degree of aged degradation of oil-immersed insulators employed in oil-filled transformers, oil-filled reactors and the like.
Recently, a mere short-period power failure can cause a great deal of damage in the circumstances in which oil-filled electrical equipments such as oil-filled transformers and oil-filled reactors are used. If an accident should happen to the oil-filled electrical equipment in these circumstances, an influence of the accident could become great. Accordingly, in order that such an accident is prevented from occurring to maintain a reliable operation, reliability of equipments and installations needs to be evaluated to apply to the maintenance of the equipments and installations and the diagnosis of the equipments and installations needs to be periodically executed with respect to the degradation of the insulation performance so that the result of the diagnosis is applied to the maintenance of the equipments and installations.
In the case of the oil-filled electrical equipments, the aged degradation of oil-immersed insulators has been conventionally diagnosed in the following method. A high polymer insulation material such as an insulating paper or press board is employed inside the oil-filled electrical equipments. A combustible gas such as CO, CH.sub.4, C.sub.2 H.sub.2 and C.sub.2 H.sub.4 or various kinds of cracked gases such as organic acid are produced with degradation of the insulation material and dissolved in the insulation oil. For the purpose of diagnosing the equipments, the insulation oil is sampled and analyzed. A total amount of CO and CO.sub.2 is measured and the diagnosis of the aged degradation is performed based on the result of measurement.
However, the measurement of the amount of CO and CO.sub.2 has conventionally been relied upon a method of detail analysis of gas dissolved in the insulation oil with a gas chromatograph. Accordingly, the measurement of the gas amount cannot be performed with ease since this method takes much time per measurement and a measuring facility is insufficient where the oil-filled electrical equipments are installed. Consequently, even when a large number of oil-filled electrical equipments need to be diagnosed at a time, the measurement of the total gas amount has to be performed for every one of the equipments, which takes much time. Thus, it is difficult to shorten intervals of the periodical total gas amount. Furthermore, the CO gas is also produced in the occurrence of localized heating or electric discharge in the interior of the equipment as well as by the aged degradation of the oil-immersed insulator. The occurrence of such internal localized heating or electric discharge can cause errors in the measurement of the total amount of gas produced with the aged degradation. Detail information is necessitated about an amount of oil-immersed insulator used in the equipment in order that this error factor is eliminated. An accurate diagnosis cannot be performed when such information cannot be obtained. Thus, an easy method of diagnosing the aged degradation or determining abnormality of the oil-filled electrical equipments has been desired.